The invention relates generally to collector heads for trolley cars.
The collector head of a current collector for a trolley car is subject to relatively large lateral forces during operation of the trolley car. The large forces, which are the result of the mass moment of inertia of the trolley pole and the trolley head, can reach approximately 130 kps during turns at high speeds. The side walls of the contact shoe, which are in contact with the overhead conductor wire, absorb these considerable forces generated by the movement of the car. Lateral forces are also generated, although of lesser severity, during periods when the car deviates laterally from the axis of the overhead conductor wire.
At turns along the trolley car path, the overhead wires intersect at sharp angles. At such corners, the sharp angles are rounded off by elastic curved rails attached to the wires to reduce the centrifugal forces acting upon the collector head. The curved rails do provide a substantially parabolic path in which the trolley car travels and reduce the magnitude of the centrifugal forces caused by sharp turns in the path. A total elimination of the lateral forces, however, is not possible and rapid increases in these lateral forces are often unavoidable. The collector head when subjected to a sudden change in direction, may lose contact with the overhead wire system during sharp turns or, for example, when the car passes rapidly under branching switches.
Swiss Pat. No. 584,116 discloses a current collector for a trolley bus having a U-shaped collector shoe support disposed at the upper end of a trolley pole. The collector shoe is rotatable about a vertical axis of the pole and is mounted so that it can pivot about a horizontal axis. During operation of the trolley bus, lateral forces are generated as described above. The collector shoe is shifted laterally with respect to the conductor axis so that the overhead conductor wire is forced against a side wall of the U-shaped collector shoe. In this way, the contact pressure between the shoe and the wire is increased, subjecting both to undesirable stresses. Accordingly, a tilting of the collector shoe may occur which tilting may cause the current collector to lose contact with the overhead wire.
It is an object of the present invention to provide a collector head for trolley cars in which the contact pressure with the overhead conductor wire is maintained at a relatively constant value.
It is a further object of the present invention to provide a collector head which prevents the contact shoe from losing contact with the overhead wire.
The present invention accomplishes these and other objects by providing a collector head in which the contact shoe and the collector base are provided with swivel joints and are connected with each other by arms which are fastened to the swivel joints. The axis of rotation of the joints extends parallel to the longitudinal axis of the contact shoe, with the distance between the axes of rotation of the collector base being greater than the distance between the axes of rotation of the contact shoe. This arrangement permits the collector base to swivel without unseating the wire from the contact shoe. At least one elastic element is disposed between the collector base and the contact shoe to damp vibration of the collector head and to restore the shoe to a normal position relative to the wire.
The collector head of the present invention provides a contact shoe which pivots about an axis that is parallel to the longitudinal axis of the contact shoe. The lateral forces, therefore, will act both in a transverse direction with respect to the shoe and downward toward the carbon contact.
The elastic element provides a restoring force for returning the contact shoe to a central position. Additionally, the elastic element also provides a resilient element which can withstand shearing stresses to provide a damping of vibrations. The swivel joints have a hingelike configuration with resilient elements placed between the moving parts of the swivel joints. The specific configuration of the joints allows the transfer of the large lateral forces and facilitates the restoring of the contact shoe to a central position. The trapezoidal placement of the collector base, the arms and the contact shoe provides a particular advantage, in that the contact shoe can pivot about the longitudinal axis of the overhead wire.